This invention relates to the field of electrodeposition of copper from aqueous solutions. In particular, the invention is concerned with an aqueous solution for the electrodeposition of copper containing additives which provide bright and leveled copper deposits, with a method for making this solution, with a method for making the additives used in the solution and with a method for electrodepositing copper employing this solution.
A large number of agents are known in the art for use, alone or in combination, in electroplating solutions to improve the quality of the electrodeposit of copper in terms of brightness, surface smoothness, hardening, leveling and to increase the lower limiting current density of deposition. A "bright" electrodeposit is an electrodeposit which has a uniform highly reflective surface gloss over substantially all of its surface, and brighteners are additives which when added to a copper electroplating solution improve the brightness of the electrodeposit. The term "leveled" denotes a copper deposit whose surface is smoother than that of its substrate. Thus, the ability of a plating bath to produce deposits relatively thicker in small recesses and relatively thinner on small protrusions thereby decreasing the depth of surface irregularities is known as "leveling." For example, a copper plating bath with satisfactory leveling ability can be utilized to reduce or eliminate the effect of microscopic cracks or scratches on the surfaces of the articles being plated.